Titanium Complexes as Vulcanization Catalysts

ABSTRACT

The invention relates to a curable composition comprising: a) at least one polymer having at least one silicon-containing group of formula —Si(R 1 ) k (Y) 3-k  as defined herein; b) at least one titanium complex of formula TiL(OR 3 ) 2  wherein each R 3  is independently selected from a C 1-20  alkyl or aryl which may optionally contain one or more heteroatoms, preferably selected from silicon, sulfur, nitrogen or oxygen atoms, wherein preferably R 3  is selected from n-butyl or isopropyl, and L is a deprotonated, tridentate ligand, and c) optionally at least one compound which has a hydrolyzable silicon-containing group and a weight average molecular weight in the range of 100 to 1000 g/mol, preparations containing these compositions and use thereof.

The invention relates to titanium compounds which are useful ascatalysts for the vulcanization of silicon-containing polymers andpolymer mixtures, and which may replace known, toxic tin compounds. Thedescribed titanium compounds are characterized by good catalyticactivity and stability, even in the presence of silane-based adhesionpromoters. In addition, suitable uses for such compounds andcompositions and preparations containing these catalysts are described.

Silicone polymers, in particular polysiloxanes such aspolydimethylsiloxane (PDMS), are of great importance in adhesives,sealants, and insulating materials. Among these materials, those whichvulcanize at low temperatures and under ambient conditions constitute aconsiderable market share. Typical formulations contain a reactive PDMSpolymer, a crosslinker, and a condensation catalyst. Although organotincompounds have been successfully used as catalysts for many years andproduce excellent results with regard to storage stability, curing time,and selectivity, they have come under criticism in recent times due totoxicological concerns and for reasons of environmental protection.

Although various metal-based catalysts have been proposed as areplacement for the well-known tin compounds, the known alternativesoften have disadvantages with regard to stability, catalytic activity,or compatibility. Titanium compounds known as a replacement have thecommon disadvantage that they are not compatible with the aminosilanesfrequently used as adhesion promoters.

Curable silicone compositions which contain siloxane polymers havinghydrolyzable end groups, titanium-based hydrolysis catalysts, andoptionally aminosilanes are known from U.S. Pat. No. 4,530,882 A, U.S.Pat. No. 5,948,854 A, and U.S. Pat. No. 5,286,766 A. The titanium-basedhydrolysis catalysts are titanium alkoxides, preferably tetraalkoxytitanates, particularly preferably tetraisopropoxy titanate. Theperformance of these catalysts is as well not completely satisfactorywith regard to their catalytic activity. In addition, the storagestability of the corresponding curable compositions is not optimal, andthe cured products obtainable therefrom have comparatively low hardness.

It is therefore an object of the present invention to providealternatives to the titanium compounds known as condensation catalysts,which overcome the known disadvantages.

The present invention achieves the object of providing improvedcondensation catalysts based on titanium to be used for curing polymerscontaining reactive silicon groups, which meet the above-describedrequirements, i.e., which have sufficient catalytic activity andstability and which are compatible with the aminosilanes customarilyused as adhesion promoters.

In a first aspect, the invention therefore relates to a curablecomposition comprising

a) at least one polymer having at least one silicon-containing group offormula (1)

—Si(R¹)_(k)(Y)_(3-k)   (1),

whereinR¹ is selected from a hydrocarbon radical containing 1 to 20 C atoms ora triorganosiloxane group of formula —O—Si(R²)₃, where each R² isindependently selected from a hydrocarbon radical containing 1 to 20 Catoms; each Y is independently selected from a hydroxy group or ahydrolyzable group, preferably an oxime group, an alkoxy group, anacetoxy group or a lactate group; andk is 0, 1, or 2;

b) at least one titanium complex of formula (2)

TiL(OR³)₂   (2),

whereineach R³ is independently selected from a C₁₋₂₀ alkyl or aryl which mayoptionally contain one or more heteroatoms, preferably selected fromsilicon, sulfur, nitrogen or oxygen atoms, wherein preferably R³ isselected from n-butyl or isopropyl;L is a deprotonated, tridentate ligand; and

c) optionally, at least one compound which has a hydrolyzablesilicon-containing group and a weight average molecular weight in therange of 100 to 1,000 g/mol measured by GPC according to DIN55672-1:2007-08, preferably the compound is an aminosilane.

In a further aspect, the invention relates to a preparation whichcontains a curable composition as described above.

The invention is further directed to the use of a composition or apreparation as defined above as an adhesive or sealant.

Yet a further aspect relates to titanium complexes of formula (2)

TiL(OR³)₂   (2),

wherein each R³ is independently selected from a C₁₋₂₀ alkyl or arylwhich may optionally contain one or more heteroatoms, preferablyselected from silicon, sulfur, nitrogen or oxygen atoms, whereinpreferably R³ is selected from n-butyl or isopropyl; and L is adeprotonated, tridentate ligand.

Lastly, the invention is further directed to the use of theabove-described titanium complexes as catalysts, in particular forcuring a silicon-containing polymer by forming siloxane bonds.

When reference is made herein to molecular weights, unless statedotherwise the reference is to the number average molecular weight, i.e.,the M_(n) value, and not the weight average molecular weight. Themolecular weight is determined by gel permeation chromatography (GPC)with tetrahydrofuran (THF) as eluent in accordance with DIN55672-1:2007-08, preferably at 35° C.

“At least one,” as used herein, means 1 or more, i.e., 1, 2, 3, 4, 5, 6,7, 8, 9, or more. With reference to an ingredient, the indication refersto the type of ingredient and not to the absolute number of molecules.“At least one polymer” thus means, for example, at least one type ofpolymer, i.e., that one type of polymer or a mixture of severaldifferent polymers may be used. Together with the weight indication, theindication refers to all compounds of the stated type which arecontained in the composition/mixture, i.e., that the compositioncontains no further compounds of this type besides the stated quantityof the compounds in question.

The term “about”, as used herein in connection with a numerical value,relates to a variance of ±20%, preferably ±10% of the respective value.

Unless explicitly stated otherwise, all percent values provided inconjunction with the compositions described herein refer to % by weight,in each case based on the mixture in question.

There are no special limitations on the polymer backbone of the at leastone polymer a), and all known polymers having various types of mainchain backbones may be used. In various embodiments, polymer a) istherefore selected from the group consisting of alkyd resins,(meth)acrylates and (meth)acrylamides and the salts thereof, phenolicresins, polyalkylenes, polyamides, polycarbonates, polyethers,polyesters, polyurethanes, vinyl polymers, polysiloxanes, andcombinations of at least two of the above-mentioned polymers.

Polyols/polyethers, in particular polyalkylene oxide, preferablypolyethylene oxide and/or polypropylene oxide, or polysiloxanes areparticularly preferably used.

According to another preferred embodiment of the composition accordingto the invention, the molecular weight M_(n) of the polymer backbone isbetween 500 and 100,000 g/mol determined by GPC in accordance with DIN55672-1:2007-08 at 35° C. Molecular weight ranges of 5000 to 25,000g/mol are particularly preferred, and of 8000 to 20,000 g/mol are veryparticularly preferred. These molecular weights are particularlyadvantageous, since compositions with these molecular weights haveviscosities which facilitate processing. The polymers may bestraight-chain or branched in each case.

The silicon-containing group in the polymer is a reactive group in whicha hydroxy group or a hydrolyzable group is bound to the silicon atom,and which is capable of crosslinking by forming a siloxane bond. Thiscrosslinking reaction may be accelerated by a silanol condensationcatalyst, such as the titanium compounds described herein.

The reactive group has the formula —Si(R¹)_(k)(Y)_(3-k), where R¹ isselected from a hydrocarbon radical containing 1 to 20 C atoms or atriorganosiloxane group of formula —O—Si(R²)₃, where each R² isindependently selected from a hydrocarbon radical containing 1 to 20 Catoms, each Y is independently selected from a hydroxy group or ahydrolyzable group, preferably an oxime group, an alkoxy group, anacetoxy group, or a lactate group, and k is 0, 1, or 2. In variousembodiments, R¹ is selected from an alkyl group containing 1 to 20 Catoms, an aryl group containing 6 to 20 C atoms, an aralkyl groupcontaining 7 to 20 C atoms, or a triorganosiloxane group of formula—O—Si(R²)₃ as defined above. If multiple Y radicals are contained, thesemay be the same or different.

Examples of hydrolyzable groups include but are not limited to ahydrogen atom, a halogen atom, an alkoxy group, an acyloxy group, anoxime group, an acetoxy group, a lactate group, an amino group, an amidegroup, an acid amide group, an aminoxy group, a mercapto group, analkenyloxy group, and the like. Alkoxy groups, in particular methoxy andethoxy groups, and oxime groups are particularly preferred. The term“oxime groups” as used herein includes ketoximes and aldoximes andrefers in general to groups which contain the functional groupR′₂C═N—O—, wherein the oxygen atom is bound to the silicon atom, and R′may be H or another group, preferably an alkyl group.

Examples of R¹ in general formula (1) described above include alkylgroups, such as a methyl group and an ethyl group, cycloalkyl groups,such as a cyclohexyl group, aryl groups, such as a phenyl group, aralkylgroups, such as a benzyl group, and a trimethylsiloxy group.

Specific examples of reactive silicon-containing groups includedimethoxymethylsilyl, diethoxymethylsilyl, and diisopropoxymethylsilylgroups.

In various embodiments, one polymer molecule in each case contains twoor more of the above-described reactive groups.

Methods for inserting reactive silicon-containing groups, preferably endgroups, into polymers are well known in the prior art.

The reactive silicon-containing group may be situated on one or bothends of the main chain, within the main chain, or within or on the endof one or more side chains.

As polymer component a), the above-described polymers may be used ineach case either alone or in combinations of two or more thereof. Ifcombinations of two or more polymers are used, the polymers that areused may differ in their monomer composition and/or their molecularweight.

The curable compositions described herein contain at least one titaniumcomplex of formula (2)

TiL(OR³)₂   (2),

wherein each R³ is independently selected from a C₁₋₂₀ alkyl or arylwhich may optionally contain one or more heteroatoms, preferablyselected from silicon, sulfur, nitrogen or oxygen atoms, whereinpreferably R³ is selected from n-butyl or isopropyl; and L is adeprotonated, tridentate ligand.

In preferred embodiments, L is a deprotonated, tridentate podand ligand.In more preferred embodiments, L is selected from the group consistingof diamidoamine of formula (3), diamidochalcogenide of formula (4), anddiamidopyridine of formula (5) in a deprotonated form,

wherein R⁴ is independently selected from a silyl group of formula—Si(R⁷)₃, where each R⁷ is independently selected from a hydrocarbonradical containing 1 to 20 C atoms, or C₁₋₂₀ alkyl or aryl which mayoptionally contain one or more heteroatoms, preferably selected fromsilicon, sulfur, nitrogen or oxygen atoms, R⁵ and R⁶ are independentlyselected from a C₁₋₂₀ alkyl or aryl which may optionally contain one ormore heteroatoms, preferably selected from silicon, sulfur, nitrogen oroxygen atoms, wherein preferably R⁴ is independently selected frommethyl, phenyl, —Si(CH₃)₃ or p-toluenesulfonyl, R⁵ and R⁶ areindependently selected from methyl or phenyl, X is a sulfur or an oxygenatom, and R⁶ is located at ortho, meta or para position relative tonitrogen. The diamidoamine of formula (3) is most preferred as theligand.

In preferred embodiments, R⁴ is independently selected from methyl,phenyl, —Si(CH₃)₃ or p-toluenesulfonyl, more preferably —Si(CH₃)₃ orp-toluenesulfonyl, most preferably p-toluenesulfonyl, and/or R⁵ and R⁶are independently selected from methyl or phenyl.

The titanium complexes are easily prepared from chlorotitanates oramidotitanates and a suitable chelating ligand. Preferred ligand is apodand ligand. Most preferred ligand is tridentate amidoamines,amidochalcogenide, diamidopyridine, or alkali salts thereof. The ligandsshould be deprotonated first by the reaction with two equivalents of abase, preferably butyl lithium.

In preferred embodiments, the titanium complex of formula (2) isprepared by coordination of the tridentate ligand of formula (3), (4),or (5) upon mixing them with a suitable titanate of the general formula(6): Ti(OR³)₂Z₂ where R³ is independently selected from a C₁₋₂₀ alkyl oraryl which may optionally contain one or more heteroatoms, preferablyselected from silicon, sulfur, nitrogen or oxygen atoms, and Z isindependently N(R⁷)₂ wherein R⁷ is independently selected from C₁₋₆alkyl, preferably methyl or ethyl, or a halide, preferably Cl. Inpreferred embodiments, R³ is independently selected from n-butyl orisopropyl.

The reaction proceeds according to the following:

wherein Y is an alkali metal such as Na, K, Li or an alkaline earthmetal such as Mg (in which case Y is MgX, where X is Cl, Br, or I),preferably Li.

In preferred embodiments, the composition also contains at least onecompound c) which has a hydrolyzable silicon-containing group and aweight average molecular weight in the range of 100 to 1000 g/molmeasured by GPC according to DIN 55672-1:2007-08. This compound is usedas a crosslinking agent, and in addition to the hydrolyzablesilicon-containing group may contain further functional groups. Thecompound may be a silane coupling agent.

This type of coupling agent may be used as a tackifier, as an agentwhich influences the physical properties, as a drying agent, as adispersion aid, or as a filler or the like. In particular, such a silanecoupling agent can act as an adhesion promoter and increase the adhesionto various surfaces, for example glass, aluminum, stainless steel, zinc,copper, mortar, PVC, acrylic resins, polyester, polyethylene,polypropylene, and polycarbonate. Such a silane coupling agent mayinclude reactive silicon-containing groups which may be definedanalogously to the groups described above in conjunction with polymercomponent a). Alternatively, the groups may also be those of formula(7):

—(Si(R¹)_(2-e)(Y)_(e)—O)_(k)—Si(R¹)_(3-d)Y_(d)   (7),

where R¹ and Y are each independently defined as above for formula (1),and e is 0, 1, or 2 and d is 0, 1, 2, or 3, where d and e are both not0, and k is 0 or an integer from 1 to 19, where d is not 0 when k is 0.

Compound c) may contain further functional groups, including but notlimited to primary, secondary, or tertiary amino groups, mercaptogroups, epoxy groups, carboxyl groups, vinyl groups, isocyanate groups,isocyanurate groups, halogens, and the like.

Specific examples of these coupling agents include but are not limitedto silanes containing Isocyanate groups, such as gamma-isocyanatepropyltrimethoxysilane, gamma-isocyanate propyltriethoxysilane,gamma-Isocyanate propylmethyldiethoxysilane, gamma-isocyanatepropylmethyldimethoxysilane, (isocyanate methyl)trimethoxysilane,(isocyanate methyl)methyldimethoxysilane, (isocyanatemethyl)triethoxysilane, and (isocyanate methyl)diethoxymethylsilane;silanes containing amino groups, such asgamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane,gamma-aminopropyltriisopropoxysilane,gamma-aminopropylmethyldimethoxysilane,gamma-aminopropylmethyldiethoxysilane,gamma-(2-aminoethyl)aminopropyltrimethoxysilane,gamma-(2-aminoethyl)aminopropylmethyldimethoxysilane,gamma-(2-aminoethyl)aminopropyltriethoxysilane,gamma-(2-aminoethyl)aminopropylmethyldiethoxysilane,gamma-(2-aminoethyl)aminopropyltriisopropoxysilane,gamma-(6-aminohexyl)aminopropyltrimethoxysilane,3-(N-ethylamino)-2-methylpropyltrimethoxysilane,gamma-ureidopropyltrimethoxysilane, gamma-ureidopropyltriethoxysilane,N-phenyl-gamma-aminopropyltrimethoxysilane,N-benzyl-gamma-aminopropyltrimethoxysilane,N-vinylbenzyl-gamma-aminopropyltriethoxysilane,N-cyclohexylaminomethyltriethoxysilane,N-cyclohexylaminomethyldiethoxymethylsilane,N-phenylaminomethyltrimethoxysilane,(2-aminoethyl)aminomethyltrimethoxysilane, andN,N′-bis[3-(trimethoxysilyl)propyl]ethylenediamine; silanes of theketimine type, such asN-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine; silanescontaining mercapto groups, such asgamma-mercaptopropyltrimethoxysilane,gamma-mercaptopropyltriethoxysilane,gamma-mercaptopropylmethyldimethoxysilane,gamma-mercaptopropylmethyldiethoxysilane,mercaptomethyltrimethoxysilane, and mercaptomethyltriethoxysilane;silanes containing epoxy groups, such asgamma-glycidoxypropyltrimethoxysilane,gamma-glycidoxypropyltriethoxysilane,gamma-glycidoxypropylmethyldimethoxysilane,beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, andbeta-(3,4-epoxycyclohexyl)ethyltriethoxysilane; carboxysilanes, such asbeta-carboxyethyltriethoxysilane,beta-carboxyethylphenylbis(2-methoxyethoxy)silane, andN-beta-(carboxymethyl)aminoethyl-gamma-aminopropyltrimethoxysilane;silanes containing unsaturated groups of the vinyl type, such asvinyltrimethoxysilane, vinyltriethoxysilane,gamma-methacryloyloxypropylmethyldimethoxysilane,gamma-acryloyloxypropyltriethoxysilane, andmethacryloyloxymethyltrimethoxysilane; silanes containing halogen, suchas gamma-chloropropyltrimethoxysilane; and isocyanurate silanes, such astris(3-trimethoxysilylpropyl)isocyanurate. In addition, partiallycondensed products or reaction products of the above-mentioned silanesmay be used. Aminosilanes selected from the group consisting ofbis(trimethylsilyl)amine, aminopropyltriethoxysilane,aminopropyltrimethoxysilane, bis[(3-triethoxysilyl)propyl]amine,bis[(3-trimethoxysilyl)propyl]amine, aminopropylmethyldiethoxysilane,aminoethylaminopropyltrimethoxysilane,aminoethylaminopropyltriethoxysilane,3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane,phenylaminomethyltrimethoxysilane,aminoethylaminopropylmethyldimethoxysilane,3-(N-phenylamino)propyltrimethoxysilane,3-piperazinylpropylmethyldimethoxysilane,3-(N,N-dimethylaminopropyl)aminopropylmethyldimethoxysilane, andcombinations of two or more of the above-mentioned compounds areparticularly preferred within the scope of the present invention.

Examples of compounds c) which contain no additional functional groupsinclude tetraalkoxysilanes (tetraalkylsilicates), such astetramethoxysilane, tetraethoxysilane, ethoxytrimethoxysilane,dimethoxydiethoxysilane, methoxytriethoxysilane, tetra-n-propoxysilane,tetra-isopropoxysilane, tetra-n-butoxysilane, tetra-isobutoxysilane, andtetra-t-butoxysilane; trialkoxysilanes, such as methyltrimethoxysilane,methyltriethoxysilane, methyltriisopropoxysilane,methyltriphenoxysilane, ethyltrimethoxysilane, butyltrimethoxysilane,and phenyltrimethoxysilane; dialkoxysilanes, such asdimethyldimethoxysilane, diethyldimethoxysilane, anddiphenyldimethoxysilane; monoalkoxysilanes, such astrimethylmethoxysilane and triphenylmethoxysilane;alkylisopropenoxysilanes, such as dimethyldiisopropenoxysilane andmethyltriisopropenoxysilane; and the partially hydrolyzed condensates ofthese silanes.

A further subject matter of the present invention is a preparation whichcontains the curable composition according to the invention. Accordingto an another preferred embodiment of the preparation according to theinvention, the preparation also contains at least one compound selectedfrom the group consisting of plasticizers, stabilizers, antioxidants,fillers, reactive diluents, drying agents, adhesion promoters, UVstabilizers, rheological aids, and/or solvents. The titanium catalystdescribed above or mixtures of various titanium catalysts, i.e.,titanium complex b), may be used in the preparation in a quantity of0.001 to about 5% by weight, preferably 0.001 to 1.5% by weight, morepreferably 0.001 to 1% by weight, most preferably 0.01 to 0.5% byweight, based on the total weight of the preparation.

The quantity of reactive polymer a) in the preparations described hereinmay be 30 to 90% by weight, more preferably 35 to 80 by weight, mostpreferably 40 to 70% by weight, based on the total weight of thepreparation. The quantity of crosslinking agent c) may be 2.5 to 7% byweight, more preferably 2.7 to 6.5 by weight, most preferably 3 to 6% byweight, based on the total weight of the preparation. Adhesion promotersmay be used in quantities of 0 to 5% by weight, more preferably 0.2 to 4by weight, based on the total weight of the preparation.

The curable compositions and preparations described herein may be usedas adhesives and sealants. This type of use is likewise part of theinvention.

It is conceivable that the viscosity of the adhesive or sealantaccording to the invention may be too high for certain applications. Theviscosity may then generally be easily and suitably reduced or adjustedby using a reactive diluent, without resulting in demixing effects (forexample, plasticizer migration) in the cured compound.

The reactive diluent preferably has at least one functional group whichreacts with moisture or atmospheric oxygen, for example, afterapplication. Examples of such groups are silyl groups, isocyanategroups, vinylically unsaturated groups, and multiply unsaturatedsystems.

All compounds which are miscible with the adhesive or sealant withreduction of the viscosity and which have at least one group that isreactive with the binder may be used as reactive diluent.

The viscosity of the reactive diluent is preferably less than 20,000mPas, particularly preferably about 0.1 to 6000 mPas, very particularlypreferably 1 to 1000 mPas (Brookfield RVT, 23° C., spindle 7, 10 rpm).

The following materials, for example, may be used as reactive diluent:polyalkylene glycols reacted with isocyanatosilanes (for example,Synalox 100-50B, DOW), carbamatopropyltrimethoxysilane,alkyltrimethoxysilanes and alkyltriethoxysilanes such asmethyltrimethoxysilane, methyltriethoxysilane, and vinyltrimethoxysilane(XL 10, Wacker), vinyltriethoxysilane, phenyltrimethoxysilane,phenyltriethoxysilane, octyltrimethoxysilane, tetraethoxysilane,vinyldimethoxymethylsilane (XL12, Wacker), vinyltriethoxysilane (GF56,Wacker), vinyltriacetoxysilane (GF62, Wacker), isooctyltrimethoxysilane(IO Trimethoxy), isooctyltriethoxysilane (IO Triethoxy, Wacker),N-trimethoxysilylmethyl-O-methylcarbamate (XL63, Wacker),N-dimethoxy(methyl)silylmethyl-O-methylcarbamate (XL65, Wacker),hexadecyltrimethoxysilane, 3-octanoylthio-1-propyltriethoxysilane, andpartial hydrolysates of these compounds.

The following polymers from Kaneka Corp. are likewise usable as reactivediluent: MS S203H, MS 5303H, MS SAT 010, and MS SAX 350.

Silane-modified polyethers which are derived, for example, from thereaction of isocyanatosilane with Synalox types may likewise be used.

Also usable as reactive diluent are polymers which are producible froman organic backbone by grafting with a vinylsilane or by reactingpolyol, polyisocyanate, and alkoxysilane.

A polyol is understood to mean a compound which may contain one or morehydroxyl (OH) groups in the molecule. The OH groups may be primary aswell as secondary.

Examples of suitable aliphatic alcohols include ethylene glycol,propylene glycol, and higher glycols, as well as other polyfunctionalalcohols. The polyols may additionally contain further functional groupssuch as esters, carbonates, and amides.

For producing the reactive diluents preferred according to theinvention, the corresponding polyol component in each case is reactedwith an at least difunctional isocyanate. As at least difunctionalisocyanate, any isocyanate having at least two isocyanate groups issuitable in principle; however, within the scope of the presentinvention, compounds having two to four isocyanate groups, in particulartwo isocyanate groups, are generally preferred.

The compound which is present as reactive diluent within the scope ofthe present invention preferably has at least one alkoxysilyl group,with the di- and trialkoxysilyl groups being preferred among thealkoxysilyl groups.

Suitable as polyisocyanates for producing a reactive diluent, forexample, are ethylene diisocyanate, 1,4-tetramethylene diisocyanate,1,4-tetramethoxybutane diisocyanate, 1,6-hexamethylene diisocyanate(HDI), cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and-1,4-diisocyanate, bis(2-isocyanatoethyl)fumarate, and mixtures of twoor more thereof,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate, IPDI), 2,4- and 2,6-hexahydrotoluylene diisocyanate,hexahydro-1,3- or -1,4-phenylene diisocyanate, benzidine diisocyanate,naphthalene-1,5-diisocyanate, 1,6-diisocyanato-2,2,4-trimethylhexane,1,6-diisocyanato-2,4,4-trimethylhexane, xylylene diisocyanate (XDI),tetramethylxylylene diisocyanate (TMXDI), 1,3- and 1,4-phenylenediisocyanate, 2,4- or 2,6-toluylene diisocyanate (TDI),2,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, or4,4′-diphenylmethane diisocyanate (MDI) or the partially or completelyhydrogenated cycloalkyl derivatives thereof, for example completelyhydrogenated MDI (H12-MDI), alkyl-substituted diphenylmethanediisocyanates, for example mono-, di-, tri-, ortetraalkyldiphenylmethane diisocyanate and partially or completelyhydrogenated cycloalkyl derivatives thereof,4,4′-diisocyanatophenylperfluoroethane, phthalicacid-bis-isocyanatoethyl ester, 1-chloromethylphenyl-2,4- or-2,6-diisocyanate, 1-bromomethylphenyl-2,4- or -2,6-diisocyanate,3,3-bis-chloromethyl ether-4,4′-diphenyl diisocyanate, sulfur-containingdiisocyanates which are obtainable by reacting 2 mol diisocyanate with 1mol thiodiglycol or dihydroxydihexylsulfide, the di- and triisocyanatesof dimer and trimer fatty acids, or mixtures of two or more of thestated diisocyanates.

Trivalent or higher-valent isocyanates, which are obtainable, forexample, by oligomerization of diisocyanates, in particular byoligomerization of the above-mentioned isocyanates, may likewise be usedas polyisocyanates. Examples of such trivalent and higher-valentpolyisocyanates are the triisocyanurates of HDI or IPDI or mixturesthereof or mixed triisocyanurates thereof, and polyphenylmethylenepolyisocyanate, which is obtainable by phosgenation ofaniline-formaldehyde condensation products.

Solvents and/or plasticizers may be used in addition to or instead of areactive diluent for reducing the viscosity of the preparation accordingto the invention.

Aliphatic or aromatic hydrocarbons, halogenated hydrocarbons, ketones,ethers, esters, ester alcohols, keto alcohols, keto ethers, keto esters,and ether esters are suitable as solvent.

The preparation according to the invention may also contain hydrophilicplasticizers. These are used for improving the moisture absorption, andthus for enhancing the reactivity at low temperatures. Suitable asplasticizers, for example, are esters of abietic acid, adipic acidesters, azelaic acid esters, benzoic acid esters, butyric acid esters,acetic acid esters, esters of higher fatty acids containingapproximately 8 to approximately 44 C atoms, esters of epoxidized fattyacids, fatty acid esters and fats, glycolic acid esters, phosphoric acidesters, phthalic acid esters, esters of linear or branched alcoholscontaining from 1 to 12 C atoms, propionic acid esters, sebacic acidesters, sulfonic acid esters, thiobutyric acid esters, trimellitic acidesters, citric acid esters, and esters based on nitrocellulose andpolyvinyl acetate, and mixtures of two or more thereof.

Suitable among the phthalic acid esters, for example, are dioctylphthalate, dibutyl phthalate, diisoundecyl phthalate, or butylbenzylphthalate, and among the adipates are dioctyl adipate, diisodecyladipate, diisodecyl succinate, dibutyl sebacate, or butyl oleate.

Likewise suitable as plasticizer are the pure or mixed ethers ofmonofunctional, linear, or branched C₄₋₁₆ alcohols or mixtures of two ormore different ethers of such alcohols, for example dioctyl ether(obtainable as Cetiol OE, Cognis Deutschland GmbH, Dusseldorf).

Polyethylene glycols which are closed by a terminal group are alsosuitable as plasticizer. Examples are polyethylene glycol orpolypropylene glycol di-C₁₋₄ alkyl ethers, in particular the dimethyl ordiethyl ethers of diethylene glycol or dipropylene glycol, and mixturesof two or more thereof.

Particularly preferred as plasticizer, however, are polyethylene glycolswhich are closed by a terminal group, such as polyethylene glycoldialkyl ethers or polypropylene glycol dialkyl ethers, wherein the alkylradical is one to four C atoms, and in particular the dimethyl anddiethyl ethers of diethylene glycol and dipropylene glycol. Inparticular, acceptable curing, even under fairly unfavorable applicationconditions (low humidity, low temperature) is achieved withdimethyldiethylene glycol. Reference is made to the relevant literaturein technical chemistry for further particulars concerning plasticizers.

Likewise suitable as plasticizer within the scope of the presentinvention are diurethanes, which may be produced, for example, byreacting diols having OH end groups with monofunctional isocyanates, byselecting the stoichiometry in such a way that essentially all free OHgroups react. Any excess isocyanate may subsequently be removed, forexample, by distillation from the reaction mixture. Another method forproducing diurethanes is to react monofunctional alcohols withdiisocyanates, with preferably all NCO groups reacting.

The preparation according to the invention may also contain up to about20% by weight of customary adhesion promoters (tackifiers). Suitable asadhesion promoters, for example, are resins, terpene oligomers,coumarone/indene resins, aliphatic petrochemical resins, and modifiedphenolic resins. Suitable within the scope of the present invention, forexample, are hydrocarbon resins which are obtained by polymerization ofterpenes, primarily α- or β-pinene, dipentene, or limonene. Thepolymerization of these monomers generally takes place cationically withinitiation with Friedel-Crafts catalysts. The terpene resins alsoinclude, for example, copolymers of terpenes and other monomers, forexample styrene, α-methylstyrene, isoprene, and the like. The statedresins are used, for example, as adhesion promoters for contactadhesives and coating materials. Likewise suited are terpene phenolicresins, which are produced by acid-catalyzed addition of phenols toterpenes or colophony. Terpene phenolic resins are soluble in mostorganic solvents and oils and miscible with other resins, waxes, andrubber. Likewise suitable as additives within the scope of the presentinvention are colophony resins and derivatives thereof, for exampleesters thereof.

Furthermore, the preparation according to the invention may additionallycontain up to about 7% by weight, in particular up to about 5% byweight, of antioxidants.

The preparation according to the invention may contain up to about 2% byweight, preferably about 1% by weight, of UV stabilizers. The so-calledhindered amine light stabilizers (HALS) are particularly suitable as UVstabilizers. Within the scope of the present invention, it is preferredto use a UV stabilizer which bears a silyl group and which isincorporated into the end product during crosslinking and curing. Theproducts Lowilite 75 and Lowilite 77 (Great Lakes, US) are particularlysuited for this purpose. In addition, benzotriazoles, benzophenones,benzoates, cyanoacrylates, acrylates, sterically hindered phenols,phosphorus, and/or sulfur may also be added.

It is often expedient to further stabilize the preparations according tothe invention against penetrating moisture by use of drying agents inorder to further extend the shelf life.

Such an improvement in the shelf life may be achieved, for example, bythe use of drying agents. All compounds which react with water to form agroup that is inert with respect to the reactive groups present in thecomposition, and which in the process preferably experience littlechange in their molecular weight, are suitable as drying agent.

Furthermore, the reactivity of the drying agents with respect tomoisture that has penetrated into the composition must be higher thanthe reactivity of the groups of the silyl group-bearing polymeraccording to the invention present in the preparation.

Isocyanates, for example, are suitable as drying agent.

Silanes are advantageously used as drying agent. Examples arevinylsilanes such as 3-vinylpropyltriethoxysilane, oxime silanes such asmethyl-O,O′,O″-butan-2-one-trioximosilane orO,O′,O″,O′″-butan-2-one-tetraoximosilane (CAS Nos. 022984-54-9 and034206-40-1), or benzamidosilanes such asbis(N-methylbenzamido)methylethoxysilane (CAS No. 16230-35-6) orcarbamatosilanes such as carbamatomethyltrimethoxysilane. However, theuse of methyl-, ethyl-, or vinyltrimethoxysilane or tetramethyl- ortetraethylethoxysilane is also possible. With regard to efficiency andcost, vinyltrimethoxysilane and tetraethoxysilane are particularlypreferred here.

Likewise suitable as drying agent are the above-mentioned reactivediluents, provided that they have a molecular weight (Mn) of less thanabout 5,000 g/mol and have end groups whose reactivity with respect topenetrated moisture is at least as high as, preferably higher than, thereactivity of the reactive groups of the silyl group-bearing polymeraccording to the invention.

Lastly, alkyl orthoformates or orthoacetates, for example methyl orethyl orthoformate, methyl or ethyl orthoacetate, may also be used asdrying agent.

The adhesives and sealants according to the invention generally containabout 0 to about 6% by weight of drying agent.

The preparation according to the invention may additionally containfillers. Suitable examples here are chalk, lime powder, precipitatedand/or pyrogenic silicic acid, zeolites, bentonites, magnesiumcarbonate, diatomaceous earth, alumina, clay, talc, titanium oxide, ironoxide, zinc oxide, sand, quartz, flint, mica, glass powder, and otherground mineral substances. In addition, organic fillers may also beused, in particular carbon black, graphite, wood fiber, wood flour,sawdust, cellulose, cotton, pulp, wood chips, chopped straw, and chaff.Moreover, short fibers such as glass fiber, glass filament,polyacrylonitrile, carbon fiber, Kevlar fiber, or also polyethylenefiber may be added. Powdered aluminum is likewise suitable as filler.

The pyrogenic and/or precipitated silicic acids advantageously have aBET surface area of 10 to 90 m²/g. During use, they do not cause anadditional increase in the viscosity of the preparation according to theinvention but contribute to strengthening of the cured preparation.

It is likewise conceivable to use pyrogenic and/or precipitated silicicacids having a larger BET surface area, advantageously 100-250 m²/g, inparticular 110-170 m²/g, as filler. Due to the larger BET surface area,the same effect, for example strengthening the cured preparation, may beobtained at a lower weight fraction. Further substances may thus be usedto improve the preparation according to the invention with regard toother requirements.

Furthermore, hollow spheres having a mineral shell or a plastic shellare suitable as filler. These may be, for example, hollow glass sphereswhich are commercially available under the trade name Glass Bubbles®.Hollow spheres based on plastic, for example Expancel® or Dualite®, aredescribed in EP 0 520 426 B1, for example. These are composed ofinorganic or organic substances, each having a diameter of 1 mm or less,preferably 500 μm or less.

For some applications, fillers are preferred which impart thixotropy tothe preparations. Such fillers are also described as rheological aids,for example hydrogenated castor oil, fatty acid amides, or swellableplastics such as PVC. To allow them to be easily pressed out of asuitable dosing device (a tube, for example), such preparations have aviscosity of 3000 to 15,000 mPas, preferably 40,000 to 80,000 mPas, oralso 50,000 to 60,000 mPas.

The fillers are preferably used in a quantity of 1 to 80% by weight,based on the total weight of the preparation.

The preparation according to the invention is produced according toknown methods by intimately mixing the components in suitable dispersionunits, for example a high-speed mixer.

A further subject matter of the present invention relates to use of thecomposition according to the invention or the preparation according tothe invention as an adhesive, sealant, or filling compound, and forproducing molded parts. A further field of application of thecompositions according to the inventions is use as plugging,hole-filling, or spackling compound.

The compositions and preparations according to the invention are thussuitable for adhesively bonding plastics, metals, glass, ceramic, wood,wood-based materials, paper, paper-based materials, rubber, andtextiles, for gluing floors, sealing building elements, windows, walland floor coverings, and jointing in general. In this regard, thematerials in each case may be adhesively bonded to themselves or withany other of the stated materials.

Lastly, the invention further relates to the use of the titanium complexas catalyst, in particular as condensation catalyst, for curing asilicon-containing polymer. During this curing, the reactivesilicon-containing groups are crosslinked to form siloxane bonds.

The following examples are used to explain the invention; however, theinvention is not limited thereto.

EXAMPLES Example 1: Preparation of Titanium Complex 1

To a stirred suspension of the ligand (formula (3),R⁴=p-toluenesulfonyl; 2.01 g, 3.54 mmol) in toluene (30 mL), which wascooled to 0° C., a solution of Ti(NEt₂)₂(n-BuO)₂ in toluene (1.12 mL,3.54 mmol) was slowly added through a dropping funnel. The reactionmixture was stirred for two hours at 0° C. before it was warmed to roomtemperature. After stirring another five hours at room temperature thereaction mixture turned orange and cleared up. The solvent wasevaporated under reduced pressure. Recrystallization fromtoluene/n-hexane gave titanium complex 1 as an orange solid.

Yield: 1.6 g (2.11 mmol, 65%).

Calculated for C₃₃H₄₇N₃O₈S₃Ti (757.80 g·mol⁻¹): C 52.30, H 6.25, N 5.54,S 12.69.

Found: C 52.18, H 6.32, N 5.98, S 12.36. ¹H NMR (500 MHz, d8-toluene,298 K): δ 0.43-0.95; (m, 6H, CH₃), 0.96-1.53; (m, 8H, CH₂), 1.58-1.64;(m, 9H, Ts-CH3), 2.96-3.64; (m, 8H, N—CH₂), 3.85-3.98; (m, 2H, O—CH₂),6.30-6.79; (m, m-Ar-H), 7.05-7.17; (m, o-Ar—H), 7.26-7.45; (m, o-Ar—H),7.00-8.00; (m, o-Ar—H). ¹³C NMR (126 MHz, d8-toluene, 298 K): δ 14.5;(CH₃), 14.5; (CH₃), 14.7; (CH₃), 19.9; (CH₂), 20.0; (CH₂), 21.3; (CH₃),21.5; (CH₃), 21.6; (CH₃), 32.4; (CH₂), 35.8; (CH₂), 48.2; (N—CH₂), 51.7;(N—CH₂), 53.5; (N—CH₂), 54.2; (N—CH₂), 75.6; (O—CH₂), 76.6; (O—CH₂),79.9; (O—CH₂), 125.8; (m-CH), 127.9; (m-CH), 130.0; (o-CH), 130.1;(o-CH), 135.7; (p-C), 135.9; (p-C), 143.2; (i-C), 143.4; (i-C), 143.7;(i-C). CI-MS m/z: 758 [M]⁺, 684 [M−^(n)BuO]⁺. IR (neat, cm⁻¹, 297 K):v=2956 (m), 2930 (m), 2868 (m).

Example 2: Preparation of Titanium Complex 2

To a stirred suspension of the ligand (formula (3),R⁴=p-toluenesulfonyl; 3.44 g, 6.08 mmol) in THF (10 mL), which wascooled to −60° C., 12.12 mmol of n-BuLi (4.85 mL of a 2.5 M solution inn-hexane) and additional 10 mL of toluene were added slowly. Afterstirring for 12 hours at room temperature the solvent was removed invacuum and an orange solid was isolated. It was suspended in toluene (10mL) and cooled to −60° C. A solution of TiCl₂(i-PrO)2 (1.45 g, 6.01mmol) in toluene (10 mL) was added drop wise. The reaction mixture waswarmed up to room temperature and stirred for 4 hours. Removing theformed LiCI by filtration and evaporating the solvent gave titaniumcomplex 2 as a slightly purple solid.

Yield: 3.89 g (5.33 mmol, 89%).

Calculated for C₃₁H₄₃N₆O₈S₃Ti (729.75 g·mol⁻¹): C 51.02, H 5.94, N 5.76,S 13.18.

Found: C 51.85, H 6.23, N 5.51, S 12.02. ¹H NMR (250 MHz, d6-benzene,298 K): δ 1.47; (d, ³J_(HH) 6.0 Hz, 12H, CH₃), 1.93; (s, 9H, CH₃), 2.89;(br s, 4H, NH₂), 3.72; (br s, 4H, N—CH₂), 5.30; (br s, 2H, O—CH), 6.78;(d, ³J_(HH) 8.0 Hz, 2H, m-Ar—H), 6.97; (d, ³J_(HH) 8.1 Hz, 4H, m-Ar—H),7.48; (d, ³J_(HH) 8.2 Hz, 2H, o-Ar—H), 8.35; (d, ³J_(HH) 8.3 Hz, 4H,o-Ar—H). ¹³C NMR (63 MHz, d6-benzene, 298 K): δ 21.2 (CH₃), 21.4; (CH₃),25.7; (CH₃), 47.5; (CH₂), 51.1; (CH₂), 82.7; (CH), 125.7; (m-CH), 129.3;(m-CH), 129.6; (o-CH), 129.6; (o-CH), 135.5; (p-C), 138.9; (p-C), 142.7;(i-C), 143.3; (i-C). MS m/z (CI): 730 [M]⁺, 670 [M−^(i)PrO+1]⁺, 628[M−2^(i)PrO+1]⁺, 574 [M−Ts]⁺. IR (neat, cm⁻¹, 297 K): v=2928 (m), 2925(m), 2892 (m).

Example 3: Preparation of Titanium Complex 3

The ligand (formula (3), R⁴=trimethylsilyl; 1.32 g, 4.11 mmol) wasdissolved in toluene (10 mL) and cooled to −55 ° C. with stirring. 8.22mmol of n-BuLi (3.3 mL of a 2.5 M solution in n-hexane) and additional 7mL of toluene were added slowly to the chilled solution giving a whiteprecipitate. The suspension was stirred for 24 hours and then cooled to−40° C. A colourless solution of TiCl₂(i-PrO)₂ (0.97 g, 4.11 mmol) intoluene (3 mL) was added drop wise. After stirring at room temperaturefor 72 hours the toluene was removed in vacuum. The residue wasdissolved in n-heptane. Removing the precipitating LiCl by filtrationand evaporating the solvent gave titanium complex 3 as a deeply redliquid.

Yield: 1.20 g (2.48 mmol, 60%).

Calculated for C₁₉H₄₉N₃O₂Si₃Ti (483.73 g·mol⁻¹): C 47.18, H 10.21, N8.69. Found: C 40.88, H 9.34, N 9.29. ¹H NMR (300 MHz, d6-benzene, 298K): δ 0.10-0.44; (m, 27H, 3·TMS), 1.20-1.39; (m, 12H, CH₃), 2.43-3.98;(m, 8H, N—CH₂) 2.48; (t, 2H, N—CH₂), 3.39; (t, 2H, N—CH₂), 4.50-4.69;(m, 1H, O—CH), 4.72-4.90; (m, 1H, O—CH). ¹³C NMR (75 MHz, d6-benzene,298 K): δ 0.8; (TMS), 1.6; (2·TMS), 27.2; (CH₃), 52.7; (CH₂), 56.1;(CH₂), 76.7; (CH).). ²⁹Si NMR (59.6 MHz, d6-benzene, 298 K): δ 0.33,1.93, 5.20, 15.51. MS m/z (CI): 484 [M]⁺, 468 [M−CH₃]⁺, 424 [M^(i)PrO]⁺,382 [M—O^(i)Pr+CH₃]⁺, 320 [2b]⁺. IR (neat, cm⁻¹, 297 K): v=2955 (m),2896 (m), 2863 (m).

Example 4: Curing Performance Test

The synthesized titanium complexes were tested in the crosslinkingreaction of a silicone mixture consisting ofα,ω-di-dialkoxyvinylsilyl-polydimethylsiloxane with a viscosity of about80,000 cST (synthesized according to U.S. Pat. No. 5,663,269 A, 71%),polydimethylsiloxane with a viscosity of about 100 cST (17%), and fumedsilica (Aerosil® R 104, Evonik, 11%). 35 g of the uncured silicone massand 1.385 mmol of the catalyst. The components were mixed in a dualasymmetric centrifugal mixer (SpeedMixer™ DAC 150.1 FVZ-K) at 3000 RPMfor 150 seconds. Test strips of the silicone mixture were made andallowed to cure under the standard atmosphere.

The skin-over time (SOT) and the depth of cure (DOC) after 24 h weremeasured following international quality standards. Skin-over time (SOT)is defined as the time required for the material to form a non-tackysurface film. The determination of the skin over time is carried outaccording to DIN 50014 under standard climate conditions (23+/−2° C.,relative humidity 50+/−5%). The temperature of the sealant must be23+/−2° C., with the sealant stored for at least 24 h beforehand in thelaboratory. The sealant is applied to a sheet of paper and spread outwith a putty knife to form a skin (thickness about 2 mm, width about 7cm). The stopwatch is started immediately. At intervals, the surface istouched lightly with the fingertip and the finger is pulled away, withsufficient pressure on the surface that an impression remains on thesurface when the skin formation time is reached. The skin-over time isreached when sealing compound no longer adheres to the fingertip. Theskin-over time is expressed in minutes.

Depth of cure (DOC) is measured as the thickness of the cured materialin a 1 cm-high probe according to ISO 4049.

TABLE 1 Curing performance of different complexes in silicone rubbers.Complex SOT [min] DOC [mm] Titanium complex 1 according to Example 1 5-73.0 Titanium complex 2 according to Example 2  6 4.0 Titanium complex 3according to Example 3 4-5 4.1 Ti(n-BuO)₄ (Comparative example 1)  8 2.7DOTL* (Comparative example 2) 10 3.6 *DOTL: dioctyltin laureate

1. A curable composition comprising a) a polymer having at least one silicon-containing group of formula (1) —Si(R¹)_(k)(Y)_(3-k)   (1), wherein R¹ is selected from a hydrocarbon radical containing 1 to 20 C atoms or a triorganosiloxane group of formula —O—Si(R²)₃, where each R² is independently selected from a hydrocarbon radical containing 1 to 20 C atoms; each Y is independently selected from a hydroxy group or a hydrolyzable group; and k is 0, 1, or 2; b) at least one titanium complex of formula (2) TiL(OR³)₂   (2), wherein each R³ is independently selected from a C₁₋₂₀ alkyl or aryl which may optionally contain one or more heteroatoms or silicon atoms; and L is a deprotonated, tridentate ligand; and c) optionally a compound which has a hydrolyzable silicon-containing group and a weight average molecular weight in the range of 100 to 1,000 g/mol measured by GPC according to DIN 55672-1:2007-08.
 2. The curable composition according to claim 1, wherein each Y is independently selected from an oxime group, an alkoxy group, an acetoxy group or a lactate group.
 3. The curable composition according to claim 1, wherein R³ is selected from n-butyl or isopropyl.
 4. The curable composition according to claim 1, wherein c) the compound which has a hydrolyzable silicon-containing group is an aminosilane.
 5. The curable composition according to claim 1, wherein polymer a) has a polymer backbone that is selected from the group consisting of alkyd resin, (meth)acrylate, (meth)acrylate salt, (meth)acrylamide, (meth)acrylamide salt, phenolic resin, polyalkylene, polyamide, polycarbonate, polyether, polyester, polyurethane, vinyl polymer, siloxane, and combinations of at least two of the above-mentioned polymers.
 6. The curable composition according to claim 1, wherein L is selected from the group consisting of diamidoamine of formula (3), diamidochalcogenide of formula (4), and diamidopyridine of formula (5), all in a deprotonated form,

wherein R⁴ is independently selected from a silyl group of formula —Si(R⁷)₃, where each R⁷ is independently selected from a hydrocarbon radical containing 1 to 20 C atoms, or a C₁₋₂₀ alkyl or aryl which may optionally contain one or more heteroatoms or silicon atoms, R⁵ and R⁶ are independently selected from a C₁₋₂₀ alkyl or aryl which may optionally contain one or more heteroatoms or silicon atoms, X is a sulfur or an oxygen atom, and R⁶ is located at ortho, meta or para position relative to nitrogen.
 7. The curable composition according to claim 6, wherein each R⁴ is independently selected from methyl, phenyl, —Si(CH₃)₃ or p-toluenesulfonyl.
 8. The curable composition according to claim 6, wherein R⁵ and R⁶ are independently selected from methyl or phenyl.
 9. The curable composition according to claim 1, wherein c) the compound which has a hydrolyzable silicon-containing group is selected from the group consisting of bis(trimethylsilyl)amine, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, bis[(3-triethoxysilyl)propyl]amine, bis[(3-trimethoxysilyl)propyl]amine, aminopropylmethyldiethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropyltriethoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane, phenylaminomethyltrimethoxysilane, aminoethylaminopropylmethyldimethoxysilane, 3-(N-phenylamino)propyltrimethoxysilane, 3-piperazinylpropylmethyldimethoxysilane, 3-(N,N-dimethylaminopropyl)aminopropylmethyldimethoxysilane, and combinations of two or more of the above-mentioned compounds
 10. The curable composition according to claim 1, being free of metal catalysts other than the b) at least one titanium complex of formula (2)
 11. A preparation containing the curable composition according to claim
 1. 12. A preparation containing the curable composition according to claim 1 and further containing at least one compound selected from the group consisting of plasticizer, stabilizer, antioxidant, filler, reactive diluent, drying agent, adhesion promoter, UV stabilizer, rheological agent, solvent and mixtures thereof.
 13. A method of curing a silicon-containing polymer by forming siloxane bonds, comprising: providing the silicon-containing polymer providing a titanium complex catalyst of formula (2) TiL(OR³)₂   (2), wherein each R³ is independently selected from a C₁₋₂₀ alkyl or aryl which may optionally contain one or more heteroatoms or silicon, or R³ is selected from n-butyl or isopropyl; L is a tridentate ligand selected from the group consisting of diamidoamine of formula (3), diamidochalcogenide of formula (4), and diamidopyridine of formula (5), all in a deprotonated form,

wherein R⁴ is independently selected from a silyl group of formula —Si(R⁷)₃, where each R⁷ is independently selected from a hydrocarbon radical containing 1 to 20 C atoms, or C₁₋₂₀ alkyl or aryl which may optionally contain one or more heteroatoms or silicon atoms, R⁵ and R⁶ are independently selected from a C₁₋₂₀ alkyl or aryl which may optionally contain one or more heteroatoms or silicon atoms; mixing the silicon-containing polymer and the titanium complex catalyst of formula (2) to form a curable, catalysed mixture; and exposing the curable, catalysed mixture to conditions under which siloxane bonds are formed.
 14. The method of claim 13 wherein R⁴ is independently selected from methyl, phenyl, —Si(CH₃)₃ or p-toluenesulfonyl, R⁵ and R⁶ are independently selected from methyl or phenyl, X is a sulfur or an oxygen atom, and R⁶ is located at ortho, meta or para position relative to nitrogen.
 15. The method of claim 13 wherein the curable, catalysed mixture is exposed to moisture to form siloxane bonds. 